1 files changed, 95 insertions, 0 deletions
diff --git a/vendor/github.com/opencontainers/runc/libcontainer/utils/cmsg.go b/vendor/github.com/opencontainers/runc/libcontainer/utils/cmsg.go
new file mode 100644
index 000000000..2cbb6491a
--- /dev/null
+++ b/vendor/github.com/opencontainers/runc/libcontainer/utils/cmsg.go
@@ -0,0 +1,95 @@
+// +build linux
+
+package utils
+
+/*
+ * Copyright 2016, 2017 SUSE LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import (
+	"fmt"
+	"os"
+
+	"golang.org/x/sys/unix"
+)
+
+// MaxSendfdLen is the maximum length of the name of a file descriptor being
+// sent using SendFd. The name of the file handle returned by RecvFd will never
+// be larger than this value.
+const MaxNameLen = 4096
+
+// oobSpace is the size of the oob slice required to store a single FD. Note
+// that unix.UnixRights appears to make the assumption that fd is always int32,
+// so sizeof(fd) = 4.
+var oobSpace = unix.CmsgSpace(4)
+
+// RecvFd waits for a file descriptor to be sent over the given AF_UNIX
+// socket. The file name of the remote file descriptor will be recreated
+// locally (it is sent as non-auxiliary data in the same payload).
+func RecvFd(socket *os.File) (*os.File, error) {
+	// For some reason, unix.Recvmsg uses the length rather than the capacity
+	// when passing the msg_controllen and other attributes to recvmsg.  So we
+	// have to actually set the length.
+	name := make([]byte, MaxNameLen)
+	oob := make([]byte, oobSpace)
+
+	sockfd := socket.Fd()
+	n, oobn, _, _, err := unix.Recvmsg(int(sockfd), name, oob, 0)
+	if err != nil {
+		return nil, err
+	}
+
+	if n >= MaxNameLen || oobn != oobSpace {
+		return nil, fmt.Errorf("recvfd: incorrect number of bytes read (n=%d oobn=%d)", n, oobn)
+	}
+
+	// Truncate.
+	name = name[:n]
+	oob = oob[:oobn]
+
+	scms, err := unix.ParseSocketControlMessage(oob)
+	if err != nil {
+		return nil, err
+	}
+	if len(scms) != 1 {
+		return nil, fmt.Errorf("recvfd: number of SCMs is not 1: %d", len(scms))
+	}
+	scm := scms[0]
+
+	fds, err := unix.ParseUnixRights(&scm)
+	if err != nil {
+		return nil, err
+	}
+	if len(fds) != 1 {
+		return nil, fmt.Errorf("recvfd: number of fds is not 1: %d", len(fds))
+	}
+	fd := uintptr(fds[0])
+
+	return os.NewFile(fd, string(name)), nil
+}
+
+// SendFd sends a file descriptor over the given AF_UNIX socket. In
+// addition, the file.Name() of the given file will also be sent as
+// non-auxiliary data in the same payload (allowing to send contextual
+// information for a file descriptor).
+func SendFd(socket, file *os.File) error {
+	name := []byte(file.Name())
+	if len(name) >= MaxNameLen {
+		return fmt.Errorf("sendfd: filename too long: %s", file.Name())
+	}
+	oob := unix.UnixRights(int(file.Fd()))
+
+	return unix.Sendmsg(int(socket.Fd()), name, oob, nil, 0)
+}